I agree with Trekker4747 and Maestro's sentiments that the singing of the National Anthem should be about the song and not so much about it being a showcase for the performer. Personally, I do not care for the extra vocal gymnastics and "warbling" that some singers add to the anthem. I would prefer to hear someone with a good voice simply singing the song "straight".
On a separate point, however, I must disagree strongly with those who claim that singing the lyrics incorrectly can only be the result of either not knowing the words well to begin with, or doing a poor job in 'cramming' to learn them at the last minute.
I feel that those holding these views about forgetting words probably do not have any public speaking, or stage or singing performance in their background. I do not care if you are Frank Sinatra or Joe Shmo from some community theater. We are all human. We sometimes mess up and forget lines or lyrics, and BELIEVE ME you have no choice as to whether it occurs while you are singing songs at some reunion of old classmates or during your big solo at the Kennedy Center. Makes no difference how many times you have sung the lyrics.
It has happened to me. It feels like a cold icicle being driven up your spine. It is like turning a page in your personal photo album and being stunned as you see someone has mysteriously removed all the photos from those pages. As my friend would say, "Brain Fart!"
If you are really good, you probably don't forget words, but I suspect it does happen to most everyone in entertainment, including high paid professional performers.
(I find it curious that I haven't seen a thread discussing how unpatriotic it was that during the Super Bowl certain high-paid, professional athletes that practice their skills on a very regular basis messed up and dropped passes that day....)
Perhaps the focus on adding extra notes and syllables did create a sort of distraction that lead to getting lost in the actual lyrics, but this does not make Christina Aguilera evil or possessing bad intent.